From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 907CFC4332F for ; Mon, 14 Nov 2022 11:44:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236440AbiKNLoE (ORCPT ); Mon, 14 Nov 2022 06:44:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40546 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236427AbiKNLoB (ORCPT ); Mon, 14 Nov 2022 06:44:01 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 05EA317079 for ; Mon, 14 Nov 2022 03:44:01 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9867D61029 for ; Mon, 14 Nov 2022 11:44:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 15CD5C4314F; Mon, 14 Nov 2022 11:43:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668426240; bh=fqd76LHS4zm9yigkSD8GcXuhYRdtL6d9jVg6IEleNpk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=X+HiDymiRneMmutFCHHvvrzFAnxG9Dq0+mCVxsufGjfUTGM/YEFWmQkgjxDWf1mL6 ShTjzuG7e9ij94oNB8sexozmUuT8PeNan6720Nwi3Zrf9bY/g3p+aITf2OEv0IBwBR ninnop3pWqIQ1ZcNpA+PrmSMAY4lx9rE3hIPHzl4zfWhsQ2Rnt9EL3OJXqef9aut72 V/YMZP1R0ltq3rg9sJABcAgRfxwQA+UhVteLabRAlscyHksSeRVfxVNa/Xu6zy+6vr jKv25Vh7nS+lZp8KqvAbUdVw/M3iorTIGV0Ch4ydgD6tULMsb1fh7DXvMF9gmuNvhF UwqHB7wWMMNWg== From: "Jiri Slaby (SUSE)" To: linux-kernel@vger.kernel.org Cc: Alexander Lobakin , Jiri Slaby Subject: [PATCH 01/46] x86/boot: robustify calling startup_{32,64}() from the decompressor code Date: Mon, 14 Nov 2022 12:42:59 +0100 Message-Id: <20221114114344.18650-2-jirislaby@kernel.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221114114344.18650-1-jirislaby@kernel.org> References: <20221114114344.18650-1-jirislaby@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Alexander Lobakin After commit ce697ccee1a8 ("kbuild: remove head-y syntax"), I started digging whether x86 is ready for removing this old cruft. Removing its objects from the list makes the kernel unbootable. This applies only to bzImage, vmlinux still works correctly. The reason is that with no strict object order determined by the linker arguments, not the linker script, startup_64 can be placed not right at the beginning of the kernel. Here's vmlinux.map's beginning before removing: ffffffff81000000 vmlinux.o:(.head.text) ffffffff81000000 startup_64 ffffffff81000070 secondary_startup_64 ffffffff81000075 secondary_startup_64_no_verify ffffffff81000160 verify_cpu and after: ffffffff81000000 vmlinux.o:(.head.text) ffffffff81000000 pvh_start_xen ffffffff81000080 startup_64 ffffffff810000f0 secondary_startup_64 ffffffff810000f5 secondary_startup_64_no_verify Not a problem itself, but the self-extractor code has the address of that function hardcoded the beginning, not looking onto the ELF header, which always contains the address of startup_{32,64}(). So, instead of doing an "act of blind faith", just take the address from the ELF header and extract a relative offset to the entry point. The decompressor function already returns a pointer to the beginning of the kernel to the Asm code, which then jumps to it, so add that offset to the return value. This doesn't change anything for now, but allows to resign from the "head object list" for x86 and makes sure valid Kbuild or any other improvements won't break anything here in general. Tested-by: Jiri Slaby Signed-off-by: Alexander Lobakin Reviewed-by: Jiri Slaby Signed-off-by: Jiri Slaby (SUSE) --- arch/x86/boot/compressed/head_32.S | 2 +- arch/x86/boot/compressed/head_64.S | 2 +- arch/x86/boot/compressed/misc.c | 16 ++++++++++------ 3 files changed, 12 insertions(+), 8 deletions(-) diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index 3b354eb9516d..56f9847e208b 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -187,7 +187,7 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) leal boot_heap@GOTOFF(%ebx), %eax pushl %eax /* heap area */ pushl %esi /* real mode pointer */ - call extract_kernel /* returns kernel location in %eax */ + call extract_kernel /* returns kernel entry point in %eax */ addl $24, %esp /* diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index d33f060900d2..aeba5aa3d26c 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -593,7 +593,7 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) movl input_len(%rip), %ecx /* input_len */ movq %rbp, %r8 /* output target address */ movl output_len(%rip), %r9d /* decompressed length, end of relocs */ - call extract_kernel /* returns kernel location in %rax */ + call extract_kernel /* returns kernel entry point in %rax */ popq %rsi /* diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index cf690d8712f4..2548d7fb243e 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -277,7 +277,7 @@ static inline void handle_relocations(void *output, unsigned long output_len, { } #endif -static void parse_elf(void *output) +static size_t parse_elf(void *output) { #ifdef CONFIG_X86_64 Elf64_Ehdr ehdr; @@ -287,16 +287,15 @@ static void parse_elf(void *output) Elf32_Phdr *phdrs, *phdr; #endif void *dest; + size_t off; int i; memcpy(&ehdr, output, sizeof(ehdr)); if (ehdr.e_ident[EI_MAG0] != ELFMAG0 || ehdr.e_ident[EI_MAG1] != ELFMAG1 || ehdr.e_ident[EI_MAG2] != ELFMAG2 || - ehdr.e_ident[EI_MAG3] != ELFMAG3) { + ehdr.e_ident[EI_MAG3] != ELFMAG3) error("Kernel is not a valid ELF file"); - return; - } debug_putstr("Parsing ELF... "); @@ -305,6 +304,7 @@ static void parse_elf(void *output) error("Failed to allocate space for phdrs"); memcpy(phdrs, output + ehdr.e_phoff, sizeof(*phdrs) * ehdr.e_phnum); + off = ehdr.e_entry - phdrs->p_paddr; for (i = 0; i < ehdr.e_phnum; i++) { phdr = &phdrs[i]; @@ -328,6 +328,8 @@ static void parse_elf(void *output) } free(phdrs); + + return off; } /* @@ -356,6 +358,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap, const unsigned long kernel_total_size = VO__end - VO__text; unsigned long virt_addr = LOAD_PHYSICAL_ADDR; unsigned long needed_size; + size_t off; /* Retain x86 boot parameters pointer passed from startup_32/64. */ boot_params = rmode; @@ -456,14 +459,15 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap, debug_putstr("\nDecompressing Linux... "); __decompress(input_data, input_len, NULL, NULL, output, output_len, NULL, error); - parse_elf(output); + off = parse_elf(output); + debug_putaddr(off); handle_relocations(output, output_len, virt_addr); debug_putstr("done.\nBooting the kernel.\n"); /* Disable exception handling before booting the kernel */ cleanup_exception_handling(); - return output; + return output + off; } void fortify_panic(const char *name) -- 2.38.1